The invention relates generally to optics, and more particularly to a pivoting element for optical applications.
Optical switches have numerous applications for optical networks in areas such as cross-connects. Micro-electro-mechanical system (MEMS) optical mirrors have been developed for use in such switches. MEMS devices are fabricated using photolithographic techniques similar to those developed for mass production of semiconductor integrated circuits. Through successive deposition of, for example, polysilicon and oxide layers onto a substrate in conjunction with masking and etching steps, a designer may form MEMS devices of myriad shapes and sizes.
In a conventional MEMS optical switch, as seen for example in U.S. Pat. No. 6,044,705, electrostatic forces are used to pivot a suspended mirror in a desired direction. In this manner, the mirror may direct light beams at a desired angle. For accurate optical switching, however, the mirror should be pivoted very precisely so that the desired angle(s) may be achieved repeatedly with high precision. The resulting angle is determined by the balance between the applied electrostatic force and the spring restoring force applied by the mirror""s suspension. This balance drifts with variations both in temperature and in stress. To prevent the drift from affecting desired results, complicated feedback circuitry is often necessary to control the direction of the mirror.
To address the need for accurate and repeatable positioning of the mirror for optical switching, U.S. Pat. No. 6,212,309 discloses a suspended rectangular mirror that pivots on its axis in the familiar manner of a playground seesaw. Just as a seesaw""s pivoting motions is stopped in the same position when it contacts the ground, the disclosed rectangular mirror will come to rest at the same angle when it is fully deflected against its substrate. Although this mirror advantageously can pivot to an accurate and repeatable direction, it suffers from certain disadvantages. For example, it has only two fully deflected positions, just as does a playground seesaw. Thus, it is limited in the number of angles in which it can direct light when in the fully deflected position.
Accordingly, there is a need in the art for a MEMS pivoting element that can accurately and repeatedly position itself in a plurality of directions.
In accordance with one embodiment of the invention, an optical switch includes an element pivotably mounted on a platform formed on a baseplate. The perimeter of the platform includes a plurality of linear segments. Electrodes are arranged on the platform such that the element may be fully deflected onto the linear segments in response to actuation forces.
In accordance with another embodiment of the invention, an optical switch includes an element pivotably mounted on a baseplate. The perimeter of the element includes a plurality of linear segments. Electrodes are arranged on the baseplate such that the element may fully deflect its linear segments onto the baseplate in response to actuation forces.